There is a clinical need for optimized fiber transmission of short pulse mid-IR laser radiation for surgical applications. Large potential markets such as skin resurfacing, dentistry, and ophthalmology utilize the Er:YSGG (2.79 mu/m) and Er:YAG (2.94 mu/m) lasers for therapeutic procedures. These lasers are capable of efficiently and precisely ablating both hard and soft tissues while avoiding the peripheral thermal damage and necrosis observed at other wavelengths. During Phase I, we developed an improved germanium fiber for short pulse and high power delivery by removal of bubbles, striation, and particles from the glass and began the development of a biocompatible fiber. Fiber transmission and fiber damage thresholds were determined at both short (500-ns) and long (8-300 us) pulse lengths, and laser parameters were optimized for efficient soft tissue ablation. Hybrid fibers consisting of silica and sapphire tips attached to a trunk fiber were developed to prevent damage of the fiber during contact tissue ablation, and tested for high power laser transmission. Phase II work will consist of six specific aims: (1) Improvement of the power handling and yield of germanium fibers by reducing remaining glass defects and improved fiber tip polishing. (2) Development of high performance and reliable germanium fibers from compositions that are biocompatible and pass the MEM cytotoxicity and intracutaneous injection tests, and study methods of fiber sterilizaton, such as autoclave and EtO. (3) Development of specialized fiber probe tip designs consisting of hybrid germanium/silica fibers, end caps, micro-lenses, side-firing fibers, and sculpted fiber tips, for flexible delivery of radiation during custom surgical procedures involving contact and non-contact laser tissue ablation. (4) Improvement of the Erbium laser spatial and temporal beam profile to provide higher fiber damage thresholds at the input/output ends of the fiber. (5) Q-switched ErYSGG transmission through fibers and specialty tips with measurement of the tissue ablation rates and quantification of the peripheral thermal and mechanical side effects. (6) Ablation of hard cataracts and precise incision of other, soft ophthalmic tissues for potential clinical applications using fiber delivery of short-pulse Er:YAG energy.